1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533
//! This crate provides a time sensitive key-value cache. When an item is inserted it is //! given a TTL. Any value that are in the cache after their duration are considered invalid //! and will not be returned on lookups. extern crate linked_hash_map; use std::borrow::Borrow; use std::cell::RefCell; use std::collections::hash_map::RandomState; use std::hash::{BuildHasher, Hash}; use std::time::{Duration, Instant}; use linked_hash_map::LinkedHashMap; #[derive(Clone)] struct Entry<V> { value: V, expiration: Instant, } impl<V> Entry<V> { fn new(v: V, duration: Duration) -> Self { Entry { value: v, expiration: Instant::now() + duration, } } fn is_expired(&self) -> bool { Instant::now() > self.expiration } } /// A time sensitive cache. #[derive(Clone)] pub struct TtlCache<K: Eq + Hash, V, S: BuildHasher = RandomState> { map: LinkedHashMap<K, Entry<V>, S>, max_size: usize, hits: RefCell<u32>, misses: RefCell<u32>, since: Instant, } impl<K: Eq + Hash, V> TtlCache<K, V> { /// Creates an empty cache that can hold at most `capacity` items. /// /// # Examples /// /// ``` /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache: TtlCache<i32, &str> = TtlCache::new(10); /// ``` pub fn new(capacity: usize) -> Self { TtlCache { map: LinkedHashMap::new(), max_size: capacity, hits: RefCell::new(0), misses: RefCell::new(0), since: Instant::now(), } } } impl<K: Eq + Hash, V, S: BuildHasher> TtlCache<K, V, S> { /// Creates an empty cache that can hold at most `capacity` items /// that expire after `duration` with the given hash builder. pub fn with_hasher(capacity: usize, hash_builder: S) -> Self { TtlCache { map: LinkedHashMap::with_hasher(hash_builder), max_size: capacity, hits: RefCell::new(0), misses: RefCell::new(0), since: Instant::now(), } } /// Check if the cache contains the given key. /// /// # Examples /// ``` /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache = TtlCache::new(10); /// cache.insert(1,"a", Duration::from_secs(30)); /// assert_eq!(cache.contains_key(&1), true); /// ``` pub fn contains_key<Q: ?Sized>(&mut self, key: &Q) -> bool where K: Borrow<Q>, Q: Hash + Eq, { // Expiration check is handled by get_mut let to_ret = self.get_mut(key).is_some(); if to_ret { self.hits.borrow_mut().saturating_add(1); } else { self.misses.borrow_mut().saturating_add(1); } to_ret } /// Inserts a key-value pair into the cache with an individual ttl for the key. If the key /// already existed and hasn't expired, the old value is returned. /// /// # Examples /// /// ``` /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache = TtlCache::new(2); /// /// cache.insert(1, "a", Duration::from_secs(20)); /// cache.insert(2, "b", Duration::from_secs(60)); /// assert_eq!(cache.get_mut(&1), Some(&mut "a")); /// assert_eq!(cache.get_mut(&2), Some(&mut "b")); /// ``` pub fn insert(&mut self, k: K, v: V, ttl: Duration) -> Option<V> { let to_insert = Entry::new(v, ttl); let old_val = self.map.insert(k, to_insert); if self.len() > self.capacity() { self.remove_oldest(); } old_val.and_then(|x| if x.is_expired() { None } else { Some(x.value) }) } /// Returns a reference to the value corresponding to the given key in the cache, if /// it contains an unexpired entry. /// /// # Examples /// /// ``` /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache = TtlCache::new(2); /// let duration = Duration::from_secs(30); /// /// cache.insert(1, "a", duration); /// cache.insert(2, "b", duration); /// cache.insert(2, "c", duration); /// cache.insert(3, "d", duration); /// /// assert_eq!(cache.get_mut(&1), None); /// assert_eq!(cache.get_mut(&2), Some(&mut "c")); /// ``` pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V> where K: Borrow<Q>, Q: Hash + Eq, { let to_ret = self.map .get(k) .and_then(|x| if x.is_expired() { None } else { Some(&x.value) }); if to_ret.is_some() { let mut x = self.hits.borrow_mut(); (*x) += 1; } else { let mut x = self.misses.borrow_mut(); (*x) += 1; } to_ret } /// Returns a mutable reference to the value corresponding to the given key in the cache, if /// it contains an unexpired entry. /// /// # Examples /// /// ``` /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache = TtlCache::new(2); /// let duration = Duration::from_secs(30); /// /// cache.insert(1, "a", duration); /// cache.insert(2, "b", duration); /// cache.insert(2, "c", duration); /// cache.insert(3, "d", duration); /// /// assert_eq!(cache.get_mut(&1), None); /// assert_eq!(cache.get_mut(&2), Some(&mut "c")); /// ``` pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V> where K: Borrow<Q>, Q: Hash + Eq, { let to_ret = self.map.get_mut(k).and_then(|x| { if x.is_expired() { None } else { Some(&mut x.value) } }); if to_ret.is_some() { let mut x = self.hits.borrow_mut(); (*x) += 1; } else { let mut x = self.misses.borrow_mut(); (*x) += 1; } to_ret } /// Removes the given key from the cache and returns its corresponding value. /// /// # Examples /// /// ``` /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache = TtlCache::new(2); /// /// cache.insert(2, "a", Duration::from_secs(30)); /// /// assert_eq!(cache.remove(&1), None); /// assert_eq!(cache.remove(&2), Some("a")); /// assert_eq!(cache.remove(&2), None); /// ``` pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V> where K: Borrow<Q>, Q: Hash + Eq, { self.map .remove(k) .and_then(|x| if x.is_expired() { None } else { Some(x.value) }) } /// Returns the maximum number of key-value pairs the cache can hold. /// /// # Examples /// /// ``` /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache: TtlCache<i32, &str> = TtlCache::new(2); /// assert_eq!(cache.capacity(), 2); /// ``` pub fn capacity(&self) -> usize { self.max_size } /// Sets the number of key-value pairs the cache can hold. Removes /// oldest key-value pairs if necessary. /// /// # Examples /// /// ``` /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache = TtlCache::new(2); /// let duration = Duration::from_secs(30); /// /// cache.insert(1, "a", duration); /// cache.insert(2, "b", duration); /// cache.insert(3, "c", duration); /// /// assert_eq!(cache.get_mut(&1), None); /// assert_eq!(cache.get_mut(&2), Some(&mut "b")); /// assert_eq!(cache.get_mut(&3), Some(&mut "c")); /// /// cache.set_capacity(3); /// cache.insert(1, "a", duration); /// cache.insert(2, "b", duration); /// /// assert_eq!(cache.get_mut(&1), Some(&mut "a")); /// assert_eq!(cache.get_mut(&2), Some(&mut "b")); /// assert_eq!(cache.get_mut(&3), Some(&mut "c")); /// /// cache.set_capacity(1); /// /// assert_eq!(cache.get_mut(&1), None); /// assert_eq!(cache.get_mut(&2), Some(&mut "b")); /// assert_eq!(cache.get_mut(&3), None); /// ``` pub fn set_capacity(&mut self, capacity: usize) { for _ in capacity..self.len() { self.remove_oldest(); } self.max_size = capacity; } /// Clears all values out of the cache pub fn clear(&mut self) { self.map.clear(); } /// Returns an iterator over the cache's key-value pairs in oldest to youngest order. /// /// # Examples /// /// ``` /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache = TtlCache::new(2); /// let duration = Duration::from_secs(30); /// /// cache.insert(1, 10, duration); /// cache.insert(2, 20, duration); /// cache.insert(3, 30, duration); /// /// let kvs: Vec<_> = cache.iter().collect(); /// assert_eq!(kvs, [(&2, &20), (&3, &30)]); /// ``` pub fn iter(&mut self) -> Iter<K, V> { self.remove_expired(); Iter(self.map.iter()) } /// Returns an iterator over the cache's key-value pairs in oldest to youngest order with /// mutable references to the values. /// /// /// # Examples /// /// ``` /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache = TtlCache::new(2); /// let duration = Duration::from_secs(30); /// /// cache.insert(1, 10, duration); /// cache.insert(2, 20, duration); /// cache.insert(3, 30, duration); /// /// let mut n = 2; /// /// for (k, v) in cache.iter_mut() { /// assert_eq!(*k, n); /// assert_eq!(*v, n * 10); /// *v *= 10; /// n += 1; /// } /// /// assert_eq!(n, 4); /// assert_eq!(cache.get_mut(&2), Some(&mut 200)); /// assert_eq!(cache.get_mut(&3), Some(&mut 300)); /// ``` pub fn iter_mut(&mut self) -> IterMut<K, V> { self.remove_expired(); IterMut(self.map.iter_mut()) } /// The cache will keep track of some basic stats during its usage that can be helpful /// for performance tuning or monitoring. This method will reset these counters. /// # Examples /// /// ``` /// use std::thread::sleep; /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache = TtlCache::new(2); /// /// cache.insert(1, "a", Duration::from_secs(20)); /// cache.insert(2, "b", Duration::from_millis(1)); /// sleep(Duration::from_millis(10)); /// let _ = cache.get_mut(&1); /// let _ = cache.get_mut(&2); /// let _ = cache.get_mut(&3); /// assert_eq!(cache.miss_count(), 2); /// cache.reset_stats_counter(); /// assert_eq!(cache.miss_count(), 0); pub fn reset_stats_counter(&mut self) { *self.hits.borrow_mut() = 0; *self.misses.borrow_mut() = 0; self.since = Instant::now(); } /// Returns the number of unexpired cache hits since the last time the counters were reset. /// # Examples /// /// ``` /// use std::thread::sleep; /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache = TtlCache::new(2); /// /// cache.insert(1, "a", Duration::from_secs(20)); /// cache.insert(2, "b", Duration::from_millis(1)); /// sleep(Duration::from_millis(10)); /// assert!(cache.get_mut(&1).is_some()); /// assert!(cache.get_mut(&2).is_none()); /// assert!(cache.get_mut(&3).is_none()); /// assert_eq!(cache.hit_count(), 1); pub fn hit_count(&self) -> u32 { *self.hits.borrow() } /// Returns the number of cache misses since the last time the counters were reset. Entries /// that have expired count as a miss. /// # Examples /// /// ``` /// use std::thread::sleep; /// use std::time::Duration; /// use ttl_cache::TtlCache; /// /// let mut cache = TtlCache::new(2); /// /// cache.insert(1, "a", Duration::from_secs(20)); /// cache.insert(2, "b", Duration::from_millis(1)); /// sleep(Duration::from_millis(10)); /// let _ = cache.get_mut(&1); /// let _ = cache.get_mut(&2); /// let _ = cache.get_mut(&3); /// assert_eq!(cache.miss_count(), 2); pub fn miss_count(&self) -> u32 { *self.misses.borrow() } /// Returns the Instant when we started gathering stats. This is either when the cache was /// created or when it was last reset, whichever happened most recently. pub fn stats_since(&self) -> Instant { self.since } // This isn't made pubic because the length returned isn't exact. It can include expired values. // If people find that they want this then I can include a length method that trims expired // entries then returns the size, but I'd rather now. One wouldn't expect a len() operation // to change the contents of the structure. fn len(&self) -> usize { self.map.len() } fn remove_expired(&mut self) { let should_pop_head = |map: &LinkedHashMap<K, Entry<V>, S>| match map.front() { Some(entry) => entry.1.is_expired(), None => false, }; while should_pop_head(&self.map) { self.map.pop_front(); } } fn remove_oldest(&mut self) -> Option<(K, V)> { self.map.pop_front().map(|x| (x.0, x.1.value)) } } pub struct Iter<'a, K: 'a, V: 'a>(linked_hash_map::Iter<'a, K, Entry<V>>); impl<'a, K, V> Clone for Iter<'a, K, V> { fn clone(&self) -> Iter<'a, K, V> { Iter(self.0.clone()) } } impl<'a, K, V> Iterator for Iter<'a, K, V> { type Item = (&'a K, &'a V); fn next(&mut self) -> Option<(&'a K, &'a V)> { match self.0.next() { Some(entry) => { if entry.1.is_expired() { self.next() } else { Some((entry.0, &entry.1.value)) } } None => None, } } fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() } } impl<'a, K, V> DoubleEndedIterator for Iter<'a, K, V> { fn next_back(&mut self) -> Option<(&'a K, &'a V)> { match self.0.next_back() { Some(entry) => { if entry.1.is_expired() { // The entries are in order of time. So if the previous entry is expired, every // else before it will be expired too. None } else { Some((entry.0, &entry.1.value)) } } None => None, } } } pub struct IterMut<'a, K: 'a, V: 'a>(linked_hash_map::IterMut<'a, K, Entry<V>>); impl<'a, K, V> Iterator for IterMut<'a, K, V> { type Item = (&'a K, &'a mut V); fn next(&mut self) -> Option<(&'a K, &'a mut V)> { match self.0.next() { Some(entry) => { if entry.1.is_expired() { self.next() } else { Some((entry.0, &mut entry.1.value)) } } None => None, } } fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() } } impl<'a, K, V> DoubleEndedIterator for IterMut<'a, K, V> { fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> { match self.0.next_back() { Some(entry) => { if entry.1.is_expired() { None } else { Some((entry.0, &mut entry.1.value)) } } None => None, } } }